Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 598D1C05027 for ; Fri, 10 Feb 2023 17:10:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232330AbjBJRKb (ORCPT ); Fri, 10 Feb 2023 12:10:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50428 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233040AbjBJRK2 (ORCPT ); Fri, 10 Feb 2023 12:10:28 -0500 Received: from relay8-d.mail.gandi.net (relay8-d.mail.gandi.net [217.70.183.201]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0445561D1E; Fri, 10 Feb 2023 09:10:26 -0800 (PST) Received: (Authenticated sender: alex@ghiti.fr) by mail.gandi.net (Postfix) with ESMTPSA id D8BAC1BF204; Fri, 10 Feb 2023 17:10:24 +0000 (UTC) Message-ID: <639b020c-7419-cbda-64c4-caffd8683131@ghiti.fr> Date: Fri, 10 Feb 2023 18:10:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH v2 00/24] Remove COMMAND_LINE_SIZE from uapi Content-Language: en-US To: Palmer Dabbelt , Arnd Bergmann , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org References: <20221211061358.28035-1-palmer@rivosinc.com> From: Alexandre Ghiti In-Reply-To: <20221211061358.28035-1-palmer@rivosinc.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 12/11/22 07:13, Palmer Dabbelt wrote: > This all came up in the context of increasing COMMAND_LINE_SIZE in the > RISC-V port. In theory that's a UABI break, as COMMAND_LINE_SIZE is the > maximum length of /proc/cmdline and userspace could staticly rely on > that to be correct. > > Usually I wouldn't mess around with changing this sort of thing, but > PowerPC increased it with a5980d064fe2 ("powerpc: Bump COMMAND_LINE_SIZE > to 2048"). There are also a handful of examples of COMMAND_LINE_SIZE > increasing, but they're from before the UAPI split so I'm not quite sure > what that means: e5a6a1c90948 ("powerpc: derive COMMAND_LINE_SIZE from > asm-generic"), 684d2fd48e71 ("[S390] kernel: Append scpdata to kernel > boot command line"), 22242681cff5 ("MIPS: Extend COMMAND_LINE_SIZE"), > and 2b74b85693c7 ("sh: Derive COMMAND_LINE_SIZE from > asm-generic/setup.h."). > > It seems to me like COMMAND_LINE_SIZE really just shouldn't have been > part of the uapi to begin with, and userspace should be able to handle > /proc/cmdline of whatever length it turns out to be. I don't see any > references to COMMAND_LINE_SIZE anywhere but Linux via a quick Google > search, but that's not really enough to consider it unused on my end. > > The feedback on the v1 seemed to indicate that COMMAND_LINE_SIZE really > shouldn't be part of uapi, so this now touches all the ports. I've > tried to split this all out and leave it bisectable, but I haven't > tested it all that aggressively. > > Changes since v1 : > * Touches every arch. > > The command line size is still an issue on riscv, any comment on this so we can make progress? Thanks, Alex